LB7 Rebuild

[MadMattMan13]

Greetings everyone. I'm new to forums and a onetime Duramax owner. Please be gentle, keep it simple and civil.
I've got a 2004 GMC Sierra 2500, regular cab. I purchased it form the original owner, a good friend. Combined, we put 325,000 miles on the truck. The truck has had two sets of Bosch injectors and a water pump. Mechanically, that's it. It's had some in cab electrical issues, but most have been addressed. A little Rotella T and some love is all its ever asked for.
That being said, it's head gasket time. The truck is in good enough shape that I would like to keep it around another 20 years. The mechanics I've spoken with have recommended a rebuilt engine swap considering the trucks miles, my desire to keep it around, and the cost of machine work. (Thoughts on this are welcome.)
Here's what I'm looking at:
- DFC LB7 Long Block
- LB7 S&S SAC Injectors
- Fleece Cheetah Turbo (has original turbo)
- New CP3 Pump
- FASS 100 Kit (never had a fuel air separator)
- Merchant Water Pump Kit
- Harmonic Balancer (brand?)
- GM Oil Cooler Kit
- Engine Mount Kit

Truck is/will be a daily driver with occasional towing. I'm not looking to do anything special but have a fun drive to work.
Your thoughts are much appreciated. Thank you for your time.

 

[2004LB7]

First off, Welcome

Second, There is no reason to need a new block at that few miles unless there was actually something wrong such as it being cracked, deeply scored cylinder walls, or something similar that would condemn the block.

If you are in need of new injectors then definitely go with SAC 00 injectors unless you want more power and plan on tuning.

Check for turbo shaft play to see if you need to replace or, better yet just rebuild it

A new CP3 might be a good idea but not always necessary. Especially if you have a lift pump and are running stock power

Do you already have a lift pump or are you looking at adding one? Hard to tell from what you said. Lift pump is great at keeping positive pressure on the CP3 and helping weak pumps and keeping air out of the lines. And maybe the best of all, priming after a fuel filter change

If you want to do the water pump then go for the stock AC Delco one. If you find one with the plastic impeller then that's good for higher RPMs

Harmonic balancer, OEM will work fine. You can always do a ATI/SoCal if you want an upgrade

I'd do the L5P oil cooler upgrade if you are thinking about doing anything to the oil cooler

Engine mounts bad? If so then OEM with a bolt through them

Are you planning on tuning or increase in power? You may need to look into a transmission rebuild if you do

 

[PureHybrid]

I'm on the same boat as just fixing the engine in it, but I'd be doing my own work. If you're paying a shop it's up to you to weigh the cost of head gaskets and machining vs engine swap. I can't see the engine swap being cost effective, as you'll still be piling up labor costs

Where in Ohio are you?

 

[08lmm72mm]

Does it have good oil pressure still and use no oil? I'd just do the headgaskets and maybe replace cp3 and injectors.

 

[Bdsankey]

Personally I would do a compression test and gauge where the motor is at overall. You will likely get skewed readings on the cyls where the HG is compromised but you can still get an average. If compression checks out decent, and it has good oil pressure, and it's not using oil I would personally do the head gaskets and keep going.


If the CP3 has never been replaced it may not be a bad time to do so for preventative measure. As for injectors, I would replace with a SAC nozzle injector, be that stock output or something like a SAC45%. SAC nozzles offer a massive lifespan improvement over the factory VCO nozzles (04.5+ use a SAC nozzle from the factory).

I would also be doing a water pump, rebuilding/replacing the turbo if it's worn, 17-19 oil cooler, LML style driver side exhaust manifold, lift pump (AirDog or FASS, lately I've been turning more and more to AirDog), Fluidampr if your harmonic balancer is worn out/needs replacement.

 

[MadMattMan13]

I'm on the same boat as just fixing the engine in it, but I'd be doing my own work. If you're paying a shop it's up to you to weigh the cost of head gaskets and machining vs engine swap. I can't see the engine swap being cost effective, as you'll still be piling up labor costs

Where in Ohio are you?

I'm just south of Canton, Ohio. New Philadelphia to be more specific.
I don't have the knowledge to do the machining that's why am/was considering the engine swap. By the time I gather the necessary parts for a rebuild and pay the machining labor I'm thinking I would be money ahead with a long block.

 

[MadMattMan13]

Does it have good oil pressure still and use no oil? I'd just do the headgaskets and maybe replace cp3 and injectors.

I thought of going this route. Oil pressure is good. The head gasket leak is leaking into the coolant system, over-pressurizing it, and forcing coolant out of the overflow reservoir. Truck runs slightly above normal operating temperature also.
You don't think I should consider redoing the main bearings and crank though given the trucks 325,000 miles? I just hate to put this amount in time and money into heads and gaskets and then spin a main bearing 10,000 miles later.

 

[MadMattMan13]

Personally I would do a compression test and gauge where the motor is at overall. You will likely get skewed readings on the cyls where the HG is compromised but you can still get an average. If compression checks out decent, and it has good oil pressure, and it's not using oil I would personally do the head gaskets and keep going.


If the CP3 has never been replaced it may not be a bad time to do so for preventative measure. As for injectors, I would replace with a SAC nozzle injector, be that stock output or something like a SAC45%. SAC nozzles offer a massive lifespan improvement over the factory VCO nozzles (04.5+ use a SAC nozzle from the factory).

I would also be doing a water pump, rebuilding/replacing the turbo if it's worn, 17-19 oil cooler, LML style driver side exhaust manifold, lift pump (AirDog or FASS, lately I've been turning more and more to AirDog), Fluidampr if your harmonic balancer is worn out/needs replacement.

Compression test is a good thought. I had not considered doing that. In its current state it does not use any oil.

 

[MadMattMan13]

First off, Welcome

Second, There is no reason to need a new block at that few miles unless there was actually something wrong such as it being cracked, deeply scored cylinder walls, or something similar that would condemn the block.

If you are in need of new injectors then definitely go with SAC 00 injectors unless you want more power and plan on tuning.

Check for turbo shaft play to see if you need to replace or, better yet just rebuild it

A new CP3 might be a good idea but not always necessary. Especially if you have a lift pump and are running stock power

Do you already have a lift pump or are you looking at adding one? Hard to tell from what you said. Lift pump is great at keeping positive pressure on the CP3 and helping weak pumps and keeping air out of the lines. And maybe the best of all, priming after a fuel filter change

If you want to do the water pump then go for the stock AC Delco one. If you find one with the plastic impeller then that's good for higher RPMs

Harmonic balancer, OEM will work fine. You can always do a ATI/SoCal if you want an upgrade

I'd do the L5P oil cooler upgrade if you are thinking about doing anything to the oil cooler

Engine mounts bad? If so then OEM with a bolt through them

Are you planning on tuning or increase in power? You may need to look into a transmission rebuild if you do

I get that my block is probably good. I was thinking I might be money ahead to buy a long block rather than pay someone to machine my old one.
I realize some of the items I'm thinking about doing are not necessary. I'm just more of proactive maintenance guy rather than reactive maintenance.
If the general consensus from this post is rebuild the top end and keep running the bottom end as is, I will likely do it. That is a huge cost savings for sure. I just hope I don't end up regretting that decision 10K miles later.
I don't plan to add anything tuning or to increase power at this point. I may do a conservative street tune later down the road but it's a daily driver, so I don't want anything crazy.

 

[TheBac]

These LB7s are tougher than nails in stock form (well, everything except the injectors).
I personally wouldnt touch the bearings. Unless your compression test shows a cylinder down, dont go into it thinking you have to do a complete rebuild. If you're worried about it, then pull the engine and check everything out first, then if you do need bearings and such, go from there.
Have the heads gone thru and decked if needed (do NOT treat these heads like gassers when machining the surface flat!)
New water pump, headgaskets, and a few misc seals. Have the turbo checked for play, replace the CP3. Definitely use SAC injectors. Id replace the balancer too. That engine will run for a long time after that.

Rebuilding an LB7 is NOT hard to do yourself. Theres just a LOT of steps involved.
You need standard wrenches and sockets, plus a 3/4" drive breaker bar, ball-socket allen head wrenches, a good torque wrench and angle meter.

One last thing -- make dang sure the shop you use knows Duramax engines and heads.

 

[MadMattMan13]

These LB7s are tougher than nails in stock form (well, everything except the injectors).
I personally wouldnt touch the bearings. Unless your compression test shows a cylinder down, dont go into it thinking you have to do a complete rebuild. If you're worried about it, then pull the engine and check everything out first, then if you do need bearings and such, go from there.
Have the heads gone thru and decked if needed (do NOT treat these heads like gassers when machining the surface flat!)
New water pump, headgaskets, and a few misc seals. Have the turbo checked for play, replace the CP3. Definitely use SAC injectors. Id replace the balancer too. That engine will run for a long time after that.

Rebuilding an LB7 is NOT hard to do yourself. Theres just a LOT of steps involved.
You need standard wrenches and sockets, plus a 3/4" drive breaker bar, ball-socket allen head wrenches, a good torque wrench and angle meter.

One last thing -- make dang sure the shop you use knows Duramax engines and heads.

Appreciate the insight. I'm starting to lean toward just a top end rebuild based on this thread. Running Rotella T, the oil has always been gold until just before the oil change interval and has never used a drop. GM and Isuzu did a pretty decent job on the LB7 if you ask me. It's not without flaws but what engine is...

 

[TheBac]

I rebuilt my LB7 in my garage. Just honed it, used cut LB7 pistons, LBZ rods, new bearings and rings. Heads were a refreshed set from Merchant (exchange). I re-used my water pump, Cp3 and balancer. Injectors were redone by a shop in town that did all our diesel injectors at work. Truck does not get driven very much any more, but it does have 65,000 miles on the rebuild and no issues other than the injectors were probably a bad idea.

 

[PureHybrid]

I'm just south of Canton, Ohio. New Philadelphia to be more specific.
I don't have the knowledge to do the machining that's why am/was considering the engine swap. By the time I gather the necessary parts for a rebuild and pay the machining labor I'm thinking I would be money ahead with a long block.

If you're doing all the other work yourself, a set of reman heads that are ready to bolt on might not be a bad idea. The only shop I could recommend out your way would be D&J down in Cambridge. They could skim your heads and pressure check them

 

[MadMattMan13]

If you're doing all the other work yourself, a set of reman heads that are ready to bolt on might not be a bad idea. The only shop I could recommend out your way would be D&J down in Cambridge. They could skim your heads and pressure check them

Thanks for the lead. Cambridge isn't to far from me.

 

[MadMattMan13]

I rebuilt my LB7 in my garage. Just honed it, used cut LB7 pistons, LBZ rods, new bearings and rings. Heads were a refreshed set from Merchant (exchange). I re-used my water pump, Cp3 and balancer. Injectors were redone by a shop in town that did all our diesel injectors at work. Truck does not get driven very much any more, but it does have 65,000 miles on the rebuild and no issues other than the injectors were probably a bad idea.

Is there a reason you used LBZ rods? Just what was laying around? Haha

 

[Bdsankey]

Is there a reason you used LBZ rods? Just what was laying around? Haha

They're a little better/stronger than 01-05 rods.

 

[GregJ77]

I rebuilt my LB7 in my garage. Just honed it, used cut LB7 pistons, LBZ rods, new bearings and rings. Heads were a refreshed set from Merchant (exchange). I re-used my water pump, Cp3 and balancer. Injectors were redone by a shop in town that did all our diesel injectors at work. Truck does not get driven very much any more, but it does have 65,000 miles on the rebuild and no issues other than the injectors were probably a bad idea.

Hey i talked to you on another thread about my truck. I'm over here hopping threads for some insight, which set of head gasket are good? I normally use mahle but I'm studding these heads and planing on building the truck this winter but I'm looking for good reputable duramax companies who sale goid stuff. I found s&s to be awesome for my sac injectors i ordered, what brand head gaskets would you fo with? On gassers (stock) i ran felpro but i am not a fan of them.

 

[Bdsankey]

Hey i talked to you on another thread about my truck. I'm over here hopping threads for some insight, which set of head gasket are good? I normally use mahle but I'm studding these heads and planing on building the truck this winter but I'm looking for good reputable duramax companies who sale goid stuff. I found s&s to be awesome for my sac injectors i ordered, what brand head gaskets would you fo with? On gassers (stock) i ran felpro but i am not a fan of them.

Mahle gaskets are top tier for these trucks. You can either get the same grade (thickness) you pulled out or you can get grade c and call it a day.

As for head fasteners, take your pick. I personally always like to use studs but for most applications new OEM TTY bolts are just fine. With studs I’ve had zero issues out of Xotics normal strength line, ARP, or DHD.


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[GregJ77]

Mahle gaskets are top tier for these trucks. You can either get the same grade (thickness) you pulled out or you can get grade c and call it a day.

As for head fasteners, take your pick. I personally always like to use studs but for most applications new OEM TTY bolts are just fine. With studs I’ve had zero issues out of Xotics normal strength line, ARP, or DHD.


Sent from my iPhone using Tapatalk

Awesome you through that xotic into the mix. Because i had arp in my cart then i been doing alot of research and hearing alot about xotic head studs. I had ARP in my cummins, but if i can get the same thing for 3 times cheaper it's worth a shot. Thanks man, Greg.

 

[TheBac]

^^^^ Brad knows what parts work best, and he can set you up with everything you need.